1. Field of the Invention
This invention relates to a remote door locking system, and in particular to a remote door locking system designed to utilize both direct transmissions such as radio frequency or optical (e.g., infrared) transmission using rolling codes, and wireless network communications.
2. Description of Related Art
Line-of-sight door locking and unlocking systems are now common in vehicles. In general, such systems utilize an infrared or radio frequency transmitter carried by the user, and a corresponding receiver connected to an integrated circuit controller capable of supplying an actuating signal to an electro-magnetic locking/unlocking mechanism built into a door of the vehicle. The controller may be a separate unit or a vehicle security system controller capable of initiating a variety of security system functions, including arming of the system and control of the engine of the vehicle.
Keyless entry systems are disclosed, for example, in U.S. Patent No. 4,931,789 (Pinnow) and U.S. Pat. No. 5,531,086 (Bryant), both of which are incorporated herein by reference, with the Pinnow patent describing an especially useful remote locking/unlocking system including a transmitter unit that may be incorporated in a portable electronic device, the display and circuitry of the electronic device being utilized to support the locking/unlocking functions. In an electronic wristwatch, for example, the power source, silicon integrated circuit chip, digital display, and battery of the electronic device serve the dual functions of telling time and generating coded signals for transmission to the electronic door locking/unlocking mechanism. The security codes in the device disclosed in this patent may be changed whenever desired by utilizing Electronically Erasable Programmable Read only Memory (EEPROM) pin-codes.
Short range radio frequency or line-of-sight communications are generally adequate for vehicle door locking/unlocking and have the advantages of simplicity, low cost operation, and convenience. In addition, line-of-sight devices have the advantage that transmission of the locking and unlocking codes cannot be intercepted and decoded unless the person challenging the system is within range of the transmitter, or has gained possession of the transmitter through loss or theft.
Nevertheless, the need for more remote actuation of vehicle security functions has led to proposals for the utilization of network communications to initiate security system functions such as alarm system arming or disarming, and disabling of the vehicle. U.S. Pat. No. 5,432,495 (Tompkins), for example, shows a system for remote locking by satellite, while U.S. Pat. No. 5,081,667 (Drori et al.) discloses what is described as a universal cellular interface for a vehicle security system and U.S. Pat. No. 5,606,307 discloses control of vehicle security functions via a pager network. In addition, U.S. Pat. No. 5,606,307 discloses a vehicle door lock controller activated by a wireless paging system. Each of these patents is incorporated by reference.
Both the systems of U.S. Pat. No. 5,432,495 and U.S. Pat. No. 5,081,667 share the principle of including in the vehicle a device that generates acoustic signals in response to receipt of radio frequency transmissions, either by satellite or over a cellular telephone network, the acoustic signals being respectively utilized by a acoustic sensor or a DTMF tone decoder to generate an electrical signal that controls a vehicle security function. However, the system of U.S. Pat. No. 5,432,495, like that of U.S. Pat. No. 5,606,307, has limited applicability because it utilizes a receiver that is capable of operating with only a single communications system, and thus require a dedicated transmitter and a subscription to a network that may not be the same as the one utilized by the owner of the vehicle for other personal communications. The system disclosed in U.S. Pat. No. 5,081,667, on the other hand, has the disadvantage that it requires a complex multiple protocol digital signal processing circuit with a relatively large memory to enable it to interface with a number of different cellular telephone systems and match the controller to the type of cellular system mounted in the vehicle. Furthermore, unlike the system of U.S. Pat. No. 4,931,781, none of the remote security system controllers includes provision for programming of codes by the user and therefore all are vulnerable to challenge by interception and recording of transmitted codes or control signals.
Of the three networked security systems described above, the one in U.S. Pat. No. 5,081,667 offers the most flexibility, but because of the complexity of the system is essentially suitable only for use in vehicles where the cost of the system might be reasonable in comparison with the cost of the vehicle being protected. For more general use, such as in a residence or in an office building or hotel with multiple doors, it would be desirable to provide a system with comparable versatility but at lower cost, and which provides for both networked and short range or line-of-sight locking/unlocking capabilities. In the case of a hotel, the ability to lock or unlock room doors from a central switch board while providing guest with individual line-of-sight transmitters would be especially advantageous.